The word for female in Spanish is femenina when used as an adjective, and mujer when referring to a female person.
Femenina is used to describe gender, such as in the phrase una palabra femenina (a feminine word). On the other hand, mujer specifically means woman, denoting an adult female human being.
Spanish is a gendered language, which means nouns and adjectives have gender. Understanding these terms can greatly enhance your Spanish vocabulary and speaking skills.